The present invention relates to a measuring device for determination of a rotary angle. More particularly, it relates to a measuring device for contactless determination of rotary angles by means of two members which are movable relative to one another and sensor coils whose resistance to alternating current is varied by relative change of the value of the regions associated with the coils and composed of electrically conductive and/or ferromagnetic material.
Measuring devices of the above mentioned general type are known in the art. One such measuring device is disclosed, for example in German document DE-OS 3,824,535.2 in which a central longitudinal groove is formed in a cylindrical coil member at its one end side. Therefore two semicircular cores are produced and a coil is wound on them. A measuring part which serves for damping is composed of an electrically conductive and/or ferromagnetic material. It surrounds at least partially the outwardly located coil regions in an axial length. An alternating current flows through the coils. By the relative rotation of the measuring part, the overlapping ratio between the measuring part and the coils is changed in an opposite direction, whereby the alternating current resistance of the coils varies correspondingly. This measuring device has the disadvantage that in the case of the movable coil core the coils cannot be wound by a winding machine one after the other. The winding technique and thereby the manufacture of the measuring device is very expensive.
Another measuring device for contactless measurement of a path and/or angle change is disclosed in German document DE-OS 3,824,534.5. In this device at least two coils are formed by an etching technique on a disc-shaped member. The etched coils can be used however only in a limited frequency region of the alternating current which flows through the coils.